Sarnoff is the managing partner at law firm Sarnoff & Baccash, a property tax appeal boutique in the Loop his father co-founded in 1986. Homeowners and businesses in Rogers Park and Lake View townships opened their mailboxes in May to see assessments valuing their property at more than they believed they could sell it for. Assessments for tax purposes normally are lower than market value.

Some of them, after the shock wore off, started looking for a lawyer.

"We've certainly received a lot more calls this cycle," Sarnoff says. While he often tells potential clients that their assessments are fair, and no appeal is filed, the valuations are "a hot issue" right ​ now. "Fear brings phone calls."

At nine lawyers, Sarnoff's firm is sizable for the type of work it handles. Lawyers at big firms rarely touch the practice, both because it is linked to electoral politics and because property tax lawyers charge contingency or flat fees, rather than billing by the hour. But there are exceptions: The Chicago Sun-Times reported that after Ald. Edward Burke severed ties with President Donald Trump's company, Mayer Brown took over five tax appeal cases representing Trump International Hotel & Tower Chicago.

The city's property tax lawyers aren't sure what to expect from Kaegi, a former mutual fund manager who, unlike Berrios, has pledged not to accept campaign donations from them. But for now, the city's triennial assessments are translating into new business, and Chicago's central business district will be assessed from Aug. 24 through Oct. 5.

In recent years, even if people or businesses thought their assessments were too high, they shrugged and chalked it up to "close enough for government work," says Thomas McNulty, a partner at Neal Gerber & Eisenberg. But since 2009, the property tax rate in the city has risen from 4.6 percent to 7.1 percent—meaning property owners pay about $7.10 for every $100 in equalized assessed value. A higher tax rate magnifies the financial impact of a higher assessment. Taxpayers can't do anything about the rate (save pay the tax and then go to court), but they can appeal the assessment.

While McNulty has yet to see a wave of clients "storming the Bastille" to appeal, he says it will crest in late summer and early autumn when notices are mailed to property owners in West, North and South townships, which each contain part of the central business district. "The tax rates are going to drive the volume of appeal," he says. "I would bet you're going to see a record."

CBRE Senior Vice President Keely Polczynski has heard from many of her clients in Lake View Township about the increase in their property tax bills. "It is a real concern . . . in some cases adversely affecting their ability to grow rents," she says in an email.

There are four places to appeal in Cook County: the assessor's office, the Cook County Board of Review, the state Property Tax Appeal Board and Circuit Court. Businesses that want to appeal to the board of review are required to have a lawyer, but residents are not.

Chicago properties were last assessed in 2015. Appeals were filed on 37 percent of all assessed parcels and 9 percent of single-family homes. (Condo buildings inflate appeal numbers because they use attorneys to appeal en masse.) Last year, when the southern suburbs were assessed, appeals hit an all-time high, at 191,611. Appeals were filed on 27 percent of all parcels and 21 percent of single-family homes.

Tom Shaer, spokesman for the assessor's office, says Berrios made the appeals process more open, including instituting online appeals, which increased the number. About half of residents do not use a lawyer when they appeal, and just over half of appeals succeed. A resident's chances of winning with a lawyer "are no better than without."

"There's a myth out there that we're there to give the attorneys business," Shaer says. "That's not true."

In fact, three years ago there weren't many cases for property tax lawyers, says Mary Nicolau, a partner in the Chicago office of Fox Rothschild.

The size of the increase in assessments and rates​ this year is driving business to Schoenberg Finkel Newman & Rosenberg as well, says Managing Partner Adam Glazer. The 23-lawyer firm has three who handle property tax appeals.

The problem with assessments that overvalue properties, Glazer jokes, is "they never make you an offer to purchase." While the city does need to fund operations, "everyone feels it should come on the back of someone else."

The property tax appeal bar doesn't know much about Kaegi beyond what he said during his campaign, says Terry Nader, a property tax appeal partner at the firm. But if he can deliver on his promise to make the system more equitable, that's what taxpayers are hoping for.